Many prior art devices are known for arresting sparks and ash and for providing ventilation in fire-containing vessels such as cooking grills and fireplaces. For example, in U.S. Pat. No. 1,537,216, a protective screen is disclosed for preventing fire from falling out of a door of a stove. The protective screen is arranged in a door opening of the stove and supported by fastening elements secured to a frame surrounding the door opening. The screen can be made of any desired mesh for the purpose intended. In one embodiment, the screen is mounted to a pivotable frame attached to the stove by hinges wherein the frame can be secured in a closed position with a rotatable latch.
In U.S. Pat. No. 1,641,022, a spark arrester is provided in the nature of a damper and regulator for fire places to retard the escape of heat up a chimney and, when closed, to prevent the ingress of insects. The spark arrester includes an elongated curved body plate with a plurality of spaced parallel slots, with the body plate being positioned to follow the curvature of the back of a brick fireplace. A second plate with a plurality of spaced parallel slots is mounted to the inner face of the body plate and is capable of slidable movement with respect to the body plate such that in an open position the slots of the body plate cooperate with the slots of the second plate and in a closed position the slots of the body plate align with the second plate.
In U.S. Pat. No. 2,722,883, a single slidable draft door is provided for controlling the degree of heat reaching a grid iron of a charcoal broiler by controlling the amount of air passing through a draft opening. The draft door is held in place and supported by slides and stops mounted to the charcoal broiler.
In U.S. Pat. No. 3,391,682, a single slide with a series of slots is slidably mounted to a slotted air vent of a charcoal broiler. The slide can be slid to cover the slots of the air vent to block the flow of air into the broiler or slid so that the slots of the slide and the slots of the air vent allow air passage through the charcoal broiler.
U.S. Pat. No. 3,851,639 discloses sliding doors provided for a portable cooking apparatus. A first single door is slide-mounted to the cooking apparatus so that it can independently be moved in one direction to completely open a related slot, moved in an opposite direction to completely close the related slot, or moved to an intermediate position. An operating tab is provided to move the door. By moving the door, burning of paper fuel in the cooking apparatus can be controlled. A second single door is provided on an oven sidewall of the cooking apparatus. The second door is mounted inside the sidewall in upper and lower slide ways and can be moved to leave an opening completely open, completely closed, or partially open to obtain intermediate temperatures in the cooking apparatus.
U.S. Pat. No. 3,915,145 discloses a single sliding door for access to a chamber of a cooking stove. The sliding door is mounted within a door slide channel. A portion of the channel is removed to provide an ash fall-off area. The door can be slid to reveal an opening for insertion of combustible materials and for provision of a bottom draft. A handle is provided on the sliding door. The door is closed after ignition of paper fuel in the stove to prevent fine newspaper ash from flying in an air draft created by rising heat. Also disclosed is a single upper vent slide gate having a handle. The upper vent slide gate closes an upper vent opening by sliding between two parallel spot-welded channels. The upper vent slide gate can be opened or closed to control air entry and regulate heat intensity inside the stove.
U.S. Pat. No. 4,587,947 discloses a sliding plate that selectively closes a central rectangular opening in a leg assembly plate of a portable grill apparatus.
In U.S. Pat. No. 5,251,607, a spark arrester is provided on the rear of a pellet-fired cooking grill. The spark arrester is perforated or slotted and mounted through a hinge on a base of a lip on the cooking grill. The spark arrester is slotted to permit air flow to support combustion.
None of the foregoing devices are completely satisfactory for arresting sparks and ash issuing from a heat source-containing vessel and none of the foregoing devices are completely satisfactory for precisely controlling ventilation and air flow to and from a heat source-containing vessel. None of the foregoing devices discloses a structure with a dual cover plate and spark arrestor both slidably movable with respect to one another.